DETAILED DESCRIPTION OF THE INVENTION
1. [Field of the invention]
The present invention relates to a stencil printing apparatus that allows normal stencil printing to be restarted at the first print sheet even after a long rest.
2. [Prior Art]
A stencil printing apparatus prints out a desired image on a print sheet by winding a stencil sheet perforated in a stencil making section on a printing drum and pinching the print paper fed from a sheet supply section between a roller and the printing drum.
Such a stencil printing apparatus, when left for a long time with no operation, often causes the ink existing on inner and outer surfaces of the drum including the openings, etc., as well as between the drum and a stencil sheet, etc. to dry.
Consequently, when a stencil making and printing operation is restarted after a long rest, it is difficult to supply a proper amount of ink onto the inner and outer surfaces of the drum and to between the drum and a stencil sheet. It is thus hardly possible to secure a normal print density at the first print sheet. The print image will thus be apt to become faint, and accordingly, quite a lot of print sheets are usually wasted until a desired print quality is obtained. This has arisen problems such as an increase in the printing cost, requirement of a long printing time, etc. The major factors of those problems are items (1) and (2) described below.
(1) The ink existing in the printing drum section, as well as between the printing drum section and a stencil sheet dries while the apparatus is at rest and a proper amount of ink for normal printing cannot be secured.
(2) The used stencil sheet for printing must be removed from the printing. drum and discharged before a newly perforated stencil sheet is wound on the printing drum. The used stencil sheet often bears considerably much ink even when it is discharged.
The viscosity of the ink used for stencil printing depends significantly on the ambient temperature, as well as on how long the apparatus is left at rest. Consequently, even when the ink is kept under a low temperature for a long time, a faint image problem often occurs.